The present invention relates to a touch type input device used in control of electronic appliance or the like, and an electronic appliance using the same.
A conventional example of capacitance type touch switch as an input device is described below while referring to a structural diagram in FIG. 16.
A capacitance type touch switch 11 as an example of capacitance type touch switch shown in FIG. 16 comprises:
a. a planar dielectric 1 made of glass or the like as base material,
b. a first conductive film 2 disposed at one side of the dielectric 1 as a flat electrode relatively wide in area so as to be touched by finger,
c. a second conductive film 3 and a third conductive film 4 disposed parallel at both sides of the dielectric 1 so as to face the first conductive film 2 on the dielectric 1 as two flat electrodes of small area,
d. a signal source 8 of pulse signal, alternating-current signal or the like connected between the second conductive film 3 and the ground 7,
e. an amplifier 9 connected to the third conductive film 4 for detecting and amplifying potential fluctuations of the third conductive film 4, and
f. a controller 10 for converting the output of the amplifier 9 into a control signal for controlling an electronic appliance (not shown).
In this constitution, the first conductive film 2 and second conductive film 3 disposed at both sides of the dielectric 1 compose a capacitance 5, and the first conductive film 2 and third conductive film 4 compose a capacitance 6.
A first conductive film 13, a second conductive film 14, and third conductive film 15 of a capacitance type touch switch 12 are provided on the same dielectric 1 as used in the aforesaid capacitance type touch switch 11. The individual conductive films of these two capacitance type touch switches 11, 12 are formed at a specific distance.
The operation of thus constituted capacitance type touch switch 11 is explained below. While the user is not touching the first conductive film 2 by finger, the signal from the signal source 8 is fed into the amplifier 9 through a series circuit of two capacitances 5 and 6. When the first conductive film 2 is touched by finger, as shown in a conceptual circuit diagram in FIG. 17, a capacitance 16 generated between the human body and the ground 7 is connected between the junction of the two capacitances 5, 6 and the ground 7. As compared with the level while the first conductive film 2 is not touched by the user""s finger, the output impedance of the signal source 8 side as seen from the amplifier 9 side is lowered, and the signal level entering the amplifier 9 is lowered.
The amplifier 9 amplifies and issues such change of signal level. The controller 10 converts the output of the amplifier 9 into a control signal for controlling the electronic appliance.
When the user touches the first conductive film 13 of the other capacitance type touch switch 12 by finger, the operation is the same as mentioned above.
However, in the capacitance type touch switch as the conventional input device, as explained above, two capacitance type touch switches 11, 12 are provided on the same dielectric 1. When the capacitance type touch switches 11 and 12 are disposed closely to each other, the capacitance 17 generated between the first conductive film 2 of the capacitance type touch switch 11 and the second conductive film 14 of the capacitance type touch switch 12 may have effects on the operation of the two capacitance type touch switches 11 and 12. Such effects on operation may lead to malfunction. To prevent this malfunction, it is hard to dispose the two capacitance type touch switches 11 and 12 closely to each other.
An input device is capable of installing the electrodes of plural touch switches on a base material in a free shape and layout.
The input device comprises:
a power transformer connected to a commercial power source,
a ground current detection circuit connected to the secondary side circuit of this power transformer and insulated from the ground,
an impedance element connected between this ground current detection circuit and the primary side circuit of the power transformer,
an operation unit having one or plural flat electrodes disposed at least on the top of a base material made of insulating material connected to the ground current detection circuit,
a control circuit connected to the ground current detection circuit, and
a display unit showing the display corresponding to the flat electrode of the operation unit.
In the thus constituted input device, touch of finger can be detected by the flat electrode disposed only at one side of the base material, and moreover plural flat electrodes can be disposed on the base material in a free shape and layout, and if plural flat electrodes are disposed closely to each other, there is no mutual effect, and an inexpensive input device is obtained.